This invention relates to form assemblies for making a wall on the peripheral wall surface of a tunnel. More particularly, this invention relates a form assemblies for use in casting concrete to make a primary covering wall on the peripheral wall surface of the tunnel. By using the unique form assemblies, the primary covering wall may be reinforced and stabilized immediately after the wall is formed.
A typical tunnel excavating system employs a shield type excavator. A which a shield of a steel-made cylinder of the excavator is driven into the ground at the tunnel face and a rotary cutter head provided in the front portion of the excavator is rotated to excavate the ground and bore the tunnel. While excavating the tunnel with such a shield type excavator, it is required to form a covering wall against the peripheral wall surface of the tunnel which extends behind the excavator as the excavator is advanced.